In the process of converting web substrates into wound parent rolls using conventional calendering and reel nip loading processes, it is known to those in the winding arts that the internal radial pressure within the parent roll increases as the number of layers is increased. As such, it is known to those in the winding industry that each layer of a wound paper web can provide pressure to each succeeding layer convolutely disposed beneath. A typical parent roll can have approximately 5,000 to 7,000 layers of wound paper disposed about a core. The end result of having so many layers is the production of pressures near the core of the wound roll that can degrade the desired properties of the paper disposed proximate to the core.
It is also known in the industry that a portion of a physical property of a tissue paper, such as caliper, can be permanently reduced if the pressure is above a known limit for the paper. Thus, the parent roll tends to lose caliper in the wound paper product that is disposed proximate to the core and radially outward several inches hence. The end effect of the resulting compression to the paper is the production of finished product rolls that do not meet desired diameter and/or winding physical property targets. Additionally, such defects in the paper substrate can cause down time in wrapping systems and could ostensibly reduce consumer appeal due to the perceived looseness of the final rolls and resulting packaging.
Several unsuccessful attempts have been made to minimize internal pressures at the core of the wound substrate. Typically, these processes provide for an adjustment of the reel nip loading to provide low pressures upon the web substrate being wound in order to preserve caliper in the finished product. This method can have several adverse effects on the parent roll structure. These adverse effects include having the substrate walk off the core, substrate shifting near the core, and the production of loosely wrapped parent rolls. These resulting parent rolls are known to be difficult to handle and can be severely out of round thereby presenting problems during the converting process.
Other techniques to provide for more uniform core winding can include providing torque at the core of the parent roll while the parent roll is being wound at the reel stage. However, these techniques provide for wrap pressures that can destroy paper properties. Modifications of such systems have been utilized by those of skill in the art; however, these modifications have not been able to eliminate caliper loss near the core of the wound substrate.
Thus, it would be desirable to provide for a coordinated calendering and parent roll winding system that provides for well wound parent rolls and is capable of preserving desired physical properties of the web substrate throughout the entirety of the wound parent roll.